1. Field Of The Invention
This invention relates to systems for obtaining access to the annulus between a well bore and a drill string herein, and particularly to a system with a plurality of valves installed in, and forming a part of, the drill string including the drill collar, whereby fluid may be pumped into the annulus as desired and which is useful for such purposes as controlling a high pressure area in the well bore resulting from the entry of high pressure formation fluid, such as a liquid or gas, into the well, a situation commonly referred to as a "kick". The valve configuration is designed for use in the drill string, but is not limited to such usage.
2. Description Of The Prior Art
Most previous downhole valves relate to cementing procedures and are not part of the drill string. An example is the apparatus of Burt, U.S. Pat. No. 2,380,022. In Burt, a plurality of valves are mounted in a conduit string such as casing or production tubing. A single manipulative device is utilized for controlling said valves. Another valve assembly usable for cementing purposes is that of Pitts, U.S. Pat. No. 3,848,670 which also utilizes a sliding valve. Still another cementing apparatus installed in the casing is shown in U.S. Pat. No. 2,249,511 to Westall.
U.S. Pat. No. 2,855,952 to Tausch et al. discloses a valve used for well stimulation and workover operations. Tausch et al. has a sliding valve member which is returned to its original position by a spring, but has a totally different opening arrangement from the valve system of the present invention.
The valve of Middleton et al., U.S. Pat. No. 2,723,677, is installed in a well string, unlike the drill string installation of the present invention, and is used for control of fluids through the well string.